The field of the invention is robotic devices to improve ambulation.
There is a need to train patients who have had spinal cord injuries or strokes to walk again. The underlying scientific basis for this approach is the observation that after a complete thoracic spinal cord transection, the hindlimbs of cats can be trained to fully support their weight, rhythmically step in response to a moving treadmill and adjust their walking speed to that of a treadmill. See for example, Edgerton et al., Recovery of full weight-supporting locomotion of the hindlimbs after complete thoracic spinalization of adult and neonatal cats. In: Restorative Neurology, Plasticity of Motoneuronal Connections. New York, Elsevier Publishers, 1991, pp. 405-418; Edgerton, et al., Does motor learning occur in the spinal cord? Neuroscientist 3:287-294, 1997b; Hodgson, et al., Can the mammalian lumbar spinal cord learn a motor task? Med. Sci. Sports Exerc. 26:1491-1497, 1994.
Relatively recently, a new rehabilitative strategy, locomotor training of locomotion impaired subjects using Body Weight Support Training (BWST) technique over a treadmill has been introduced and investigated as a novel intervention to improve ambulation following neurologic injuries. Results from several laboratories throughout the world suggest that locomotor training with a BWST technique over a treadmill significantly can improve locomotor capabilities of both acute and chronic incomplete spinal cord injured (SCI) patients.
Current BWST techniques rely on manual assistance of several therapists during therapy sessions. Therapists provide manual assistance to the legs to generate the swing phase of stepping and to stabilize the knee during stance. This manual assistance has several important scientific and functional limitations. First, the manual assistance provided can vary greatly between therapists and sessions. The patients"" ability to step on a treadmill is highly dependent upon the skill level of the persons conducting the training. Second, the therapists can only provide a crude estimate of the required force torque and acceleration necessary for a prescribed and desired stepping performance. To date all studies and evaluations of step training using BWST technique over a treadmill have been limited by the inability to quantify the joint torques and kinematics of the lower limbs during training. This information is critical to fully assess the changes and progress attributable to step training with BWST technique over a treadmill. Third, the manual method can require up to three or four physical therapists to assist the patient during each training. session. This labor-intensive protocol is too costly and impractical for widespread clinical applications.
There is a need for a mechanized system with sensor-based automatic feedback control exists to assist the rehabilitation of neurally damaged people to relearn the walking capability using the BWST technique over a treadmill. Such a system could alleviate the deficiencies implied in the currently employed manual assistance of therapists. A programmable stepper device would utilize robotic arms instead of three physical therapists. It would provide rapid quantitative measurements of the dynamics and kinematics of stepping. It would also better replicate the normal motion of walking for the patients, with consistency.
The invention is a robotic exoskeleton and a control system for driving the robotic exoskeleton. It includes the method for making and using the robotic exoskeleton and its control system. The robotic exoskeleton has sensors embedded in it which provide feedback to the control system.
The invention utilizes feedback from the motion of the legs themselves, as they deviate from a normal gait, to provide corrective pressure and guidance. The position versus time is sensed and compared to a normal gait profile. There are various normal profiles based on studies of the population for age, weight, height and other variables. While the portion of the legs is driven according to a realistic model human gait, additional mechanical assistance is applied to flexor and extensor muscles and tendons at an appropriate time in the gait motion of the legs in order to stimulate the recovery of afferent-efferent nerve pathways located in the lower limbs and in the spinal cord. The driving forces applied to move the legs are positioned to induce activations of these nerve pathways in the lower limbs that activate the major flexor and extensor muscle groups and tendons, rather than lifting from the bottom of the feet.